Salt fog corrosion behavior of friction stir welded AA2014-T651 aluminum alloy

High strength aluminum alloys of type AA2014 are used in aerospace applications. This alloy is considered unweldable using fusion welding processes. Friction stir welding being a solid state process has been proved to be a suitable process for obtaining sound welds of these materials. In the current study, 8 mm thick rolled AA2014-T651 aluminum alloy plates were joined using friction stir welding. The corrosion behavior of base material and friction stir welds was investigated using the salt fog test (ASTM B117). The corrosion resistance of the welds and parent material in the basic solution was found to be better than that in acidic and neutral solutions. It was also found that the corrosion rate increases with increase in time of exposure. It has been observed that corrosion attack is greater in the weld region than in the parent material and within the weld, heat affected zone has been found to be more susceptible to corrosion compared to the weld nugget and thermomechanically affected zone regions. Transmission electron microscopy studies revealed coarser precipitates and precipitate-free zones in the heat affected zone which are concluded to be the reasons for more susceptibility to corrosion.